This repository contains the source used to create the [Runners] for CI. To build a VM machine from this repo's source, see the instructions.

Environment	YAML Label	Included Software	Latest Release & Rollout Progress
Ubuntu 20.04	ubuntu-20.04	ubuntu-20.04
Ubuntu 18.04	ubuntu-latest or ubuntu-18.04	ubuntu-18.04
Ubuntu 16.04	ubuntu-16.04	ubuntu-16.04
macOS 11.0	macos-11.0	macOS-11.0
macOS 10.15	macos-latest or macos-10.15	macOS-10.15
Windows Server 2019	windows-latest or windows-2019	windows-2019
Windows Server 2016	windows-2016	windows-2016

The Ubuntu 20.04 virtual environment is currently provided as a preview only.
The "ubuntu-latest" YAML workflow label still uses the Ubuntu 18.04 virtual environment.

The MacOS 11.0 virtual environment is currently provided as a preview only.
The "macos-latest" YAML workflow label still uses the MacOS 10.15 virtual environment.

Looking for other Linux distributions? We do not plan to offer other Linux distributions. We recommend using Docker if you'd like to build using other distributions with the hosted virtual environments. Alternatively, you can leverage self-hosted runners and fully customize your environment to your needs.

How to contribute to macOS source? macOS source lives in this repository and available for everyone. However, MacOS image-generation CI doesn't support external contributions yet so we are not able to accept pull-requests for now. We are in the process of preparing MacOS CI to accept contributions. Until then, we appreciate your patience and ask you continue to make tool requests by filing issues.

In general, these are the guidelines we consider when deciding what to pre-install:

• Tools and ecosystems that are broadly popular and widely-used will be given priority.
• Recent versions of tools will be given priority over older versions.
• Tools and versions that are deprecated or have reached end-of-life will not be added.
• Tools and versions will typically be removed 6 months after they are deprecated or have reached end-of-life.
• If a tool can be installed during the build, we will evaluate how much time is saved and how much space is used by having the tool pre-installed.
• MIT, Apache, and GNU licenses are ok, anything else we'll have to check with lawyers.
• If a tool takes much space we will evaluate space usage and provide a decision if this tool can be pre-installed.
• If a tool requires the support of more than one version, we will consider the cost of this maintenance, how often new versions bring dangerous updates.

Note: For new tools, please, create an issue and get an approval from us to add this tool to the image before creating the pull request.